In general, if a patient has a surgical operation, he or she feels a pain around where he or she has had the surgery. Then, the degrees of pain felt by the patients are different according to the kinds of the surgical operations and operation spots, and in particular, the degrees of pain felt by the patients are different, depending on the individual characteristics of the patients even though the same kind of surgical operations are conducted.
Accordingly, together with a liquid injector (KR 10-0519247 B1) that continuously injects an analgesic to alleviate the pain of the patient, a liquid injector patient controlled analgesia (PCA) that can additionally inject an analgesic when the patient complains of pain are necessary. That is, a liquid injector is installed between a liquid supply and a catheter according to the related art, and catches and charges the liquid at an intermediate point when the liquid supply continuously sends the liquid to the catheter and additionally sends the liquid whenever it is necessary to alleviate the pain of the patient.
However, the catheter connected to the liquid injector is inserted into a vein or an epidural space of a patient to inject liquid into the body of the patient, and the catheter generally has a diameter of about 2 mm and is thin and long and thus the quantity of injected liquid is small and the injection speed of the liquid is also low.
Accordingly, the recharging time of the liquid injector for catching and charging the liquid at an intermediate point is long because the injection speed of the liquid is low, and in particular, even when the charged liquid is to be additionally introduced by pushing the button of the liquid injector, the quantity of the introduced liquid is not constant so that it is difficult to identify how much the liquid has been injected into the body of the patient.
That is, as the liquid is repeatedly injected into the body of the patient while the liquid is not completely charged, it is not identified how much the liquid corresponding to a narcotic analgesic is injected into the body of the patient.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.